Many years ago I went diving in Thailand next to one of those cliffs sticking out of water. It was the first time in my life and it was extremely difficult to fight my claustrophobia. I could only go down a couple of meters. On the second day I dove too deep! I was totally enchanted by the vertical world: corrals, fish, snakes. I just dove and dove until the instructor told me to check my pressure watch. I went to 19 meters depth, when we were planning to only do 12.
I saw the clown fish, the water snake, the dragon fish, some gigantic fish swimming below me and other animals I have only seen on TV. But in order to see some sharks, one might need to dive 30 meters. I still sometimes have dreams about it..